Another reason why you might increase speed below 10 is to catch the profile after ATC didn't descend you on time..
You should do a search,for ex for the 767 AA bird hit,at FL120,
So actually it also unsafe to accelerate above 10?
Doesn't the Goose make it somewhere until level 300?
Alex, when do you accelerate/decelerate?
If I remember well, econ descent in a 737 is often around 280 kts. So if you have a choice, why wouldn't you fly it down to final intercept? It's also a bit of a waste to always reduce to 250 -oh no, 240 to make sure you stay under 250- in all conditions.
You don't have to fly like a cowboy while at the same time being efficient in time and energy management.